(a) Field of the Invention
The present invention relates to an exhaust hood. More particularly, the invention is concerned with a hood which is used to separate grease particles contained in cooking fumes produced when cooking over a cooking unit, the fumes being directed towards the hood. The exhaust hood according to the invention is particularly interesting in that the swirling motion of the path of cooking fumes can be adjusted depending on the volume and the velocity of the fumes to be exhausted and which may contain various amounts of grease particles.
(b) Description of Prior Art
In a commercial kitchen, such as in a restaurant where the cooking units produce considerable quantities of fumes loaded with smoke, grease particles, moisture and the like, it is necessary to provide hoods over them which will return gases to the outside air which are as free as possible from undesired material. Now, since these systems must be efficient, they naturally consume a lot of energy. Moreover, since all these cooking units do not necessarily produce the same quantities of cooking fumes, it would be of interest to be able to rely on devices which consume no unnecessary energy to treat different types of fumes.
Ideally, commercial hoods induce some swirling of the flow of cooking fumes thereby trapping some of the impurities and undesired materials present therein through the action of centrifugal force which so to speak throws the impurities and undesired materials out of the path of the ascending fumes onto some traps or the walls disposed along the path of the fumes. However, due to the need to provide a very efficient system, the present exhaust hoods are often more sophisticated and energy consuming than is really needed. In reality, one selects a particular exhaust hood available on the market and has to live with it, even though in many cases it might be more performing than it is really needed.
In many types of hoods, the exhaust fan may be adjusted to cause a variation in the amount of suction it provides depending on the quantity of fumes produced and the amounts of impurities contained therein, thereby saving energy. Also, it is know that centrifugal force is responsible for causing the separation of grease particles and other impurities. Sometimes, when the volume of cooking fumes is not too important and the suction force provided by the fan is consequently not great, the swirling motion provided to the path of cooking fumes is not sufficient to rid the cooking fumes of a substantial part of its grease particles, impurities and other undesired materials. The only solution is to accelerate the speed of the fan, which is energy consuming and therefore undesirable. In other cases, if the suction applied is at a maximum, a desired swirling consequently follows and it is then unnecessary to provide additional means along the path to cause more swirling.
In addition, in order to operate a grease extracting hood economically and with good yield and maximum efficiency, it would be desirable to maintain a constant static pressure inside the hood.
The prior is loaded with references teaching various ways of producing a flow of cooking fumes which intend to remove as much undesirable materials as possible. In this connection, the following references should be noted:
U.S. Pat. No. 4,822,385 PA1 U.S. Pat. No. 4,281,635 PA1 U.S. Pat. No. 4,266,529 PA1 U.S. Pat. No. 4,071,019 PA1 U.S. Pat. No. 3,893,831 PA1 U.S. Pat. No. 3,055,285 PA1 U.S. Pat. No. 2,532,420 PA1 U.S. Pat. No. 2,081,640. PA1 means defining an upwardly directed swirling path for the cooking fumes thereby inducing centrifugal force in a flow of the cooking fumes and removing grease particles and other impurities from the cooking fumes, PA1 means permitting the removed grease particles and other impurities to drop in counter-current to the upwardly directed swirling path to be collected in the lower part of the hood, and PA1 a plurality of forwardly adjustable blade means disposed along the path to maintain a constant static pressure therein and accentuate or decrease the intensity of the swirling path and thereby of the centrifugal force applied to the grease particles and other impurities depending on the volume and flow rate of the cooking fumes ascending through the hood. PA1 means defining an upwardly inclined inlet deflector at the entrance of the flow of cooking fumes into the hood. PA1 In accordance with another preferred embodiment, the exhaust hood also comprises PA1 means defining a downwardly inclined internal deflector upwardly spaced from the inlet deflector. PA1 a manifold provided at the outer edge of the transverse plate, the manifold having cleaning jets mounted thereon to remove grease particles and other impurities remaining accumulated on the blade means, transverse plate and deflectors, by projecting a cleaning fluid thereon.
However, none of these references, teach the possibility of treating different volumes and flow rates of ascending cooking fumes to be exhausted.